Applications open twice & freeze

After recently installing Outlook2003 it worked well (& I recommend it – it’s a real upgrade, not like some of the other MS apps) & works well on the laptop. On the main PC though, it’s started opening, gets about halfway then another Outlook window opens, both freeze & can only kill via Task Manager. There are 2 X OUTLOOK.EXE in Win Task Man. (Killing one kills both). As occasionally some other apps (non-MS ones) appear to do the same, maybe Windows problem, rather than Outlook itself? I’m running Win XP Pro SP1. I did do a routine Windows update recently.